add the comments for the mcs-lock and seqlock benchmarks that we changed during the...

diff --git a/mcs-lock/mcs-lock.cc b/mcs-lock/mcs-lock.cc
index 525ef9b07a947c9fe7ccf39b4586576bff204cd9..4ae59ff6f0db56e3a0a69e9980a8d74b3b70fc79 100644 (file)
--- a/mcs-lock/mcs-lock.cc
+++ b/mcs-lock/mcs-lock.cc
@@ -77,6 +77,8 @@ void mcs_mutex::unlock(guard * I) {
         // "memory_order_relaxed", run "make" to recompile, and then run:
         // "./run.sh ./mcs-lock/testcase -m2 -Y -u3 -tSPEC"
         /**********  Detected Correctness **********/
+        // This used the stronger mo_acq_rel parameter in old versions, but this
+        // is not necessary.
                if ( m_tail.compare_exchange_strong(
                        tail_was_me,NULL,std::mo_release) ) {
                        // got null in tail, mutex is unlocked

diff --git a/seqlock/seqlock.cc b/seqlock/seqlock.cc
index ca4a55c0823e676dab31fab07f9d75d137894252..862dfd2566ad4a06a1e35a314c434c0262534653 100644 (file)
--- a/seqlock/seqlock.cc
+++ b/seqlock/seqlock.cc
@@ -20,6 +20,8 @@ void seqlock::read(int *data1, int *data2) {
                /**********    Detected Correctness (testcase1)    **********/
                int old_seq = _seq.load(memory_order_acquire); // acquire
                if (old_seq % 2 == 1) {
+            // The thrd_yield() operation is just for fairness but won't affect
+            // the correctness (and also the specification).
             thrd_yield();
             continue;
         }
@@ -35,6 +37,8 @@ void seqlock::read(int *data1, int *data2) {
                /**********    Detected Correctness (testcase1)    **********/
                atomic_thread_fence(memory_order_acquire);
                if (_seq.load(memory_order_relaxed) == old_seq) { // relaxed
+            // The thrd_yield() operation is just for fairness but won't affect
+            // the correctness (and also the specification).
             thrd_yield();
                        return;
                }
@@ -51,6 +55,8 @@ void seqlock::write(int data1, int data2) {
                /**********    Detected Correctness (testcase2 with -y -x1000)    **********/
                int old_seq = _seq.load(memory_order_acquire); // acquire
                if (old_seq % 2 == 1) {
+            // The thrd_yield() operation is just for fairness but won't affect
+            // the correctness (and also the specification).
             thrd_yield();
                        continue; // Retry
         }
@@ -58,6 +64,8 @@ void seqlock::write(int data1, int data2) {
                // #2
                if (_seq.compare_exchange_strong(old_seq, old_seq + 1,
                        memory_order_relaxed, memory_order_relaxed)) {
+            // The thrd_yield() operation is just for fairness but won't affect
+            // the correctness (and also the specification).
             thrd_yield();
                        break;
                }